Method of making arylamines



Patented Sept. 9, 1930 UNITED STATES PATENT OFFICE WILLIAM H. WILLIAMS,OF MIDLAND, MICHIGAN ASBIGNOR TO THE DO'W CHEMICAL COMPANY, OF MIDLAND,MICHIGAN, A CORPORATION OF MICHIGAN METHOD OF MAKING AR 1T0 Drawing.

Various attempts have been made toprepare arylamines om thecorresponding halogenated aromatic hydrocarbon derivatives by directreaction between the latter and am- 5 monia at an elevated temperatureand corresponding high pressure, but, so far aswe are aware, nocommercial success has attended efiorts heretofore made along this line.In the main such failure may be attributed to inability to secure aproper yield of the desired end product, so that the process isunprofitable. In certain cases where a relatively hi h yield has beenobtained it has been found upon trial that the reacting mixture has sucha destructive eiiect on the containers or apparatus in which the processis conducted as to render such processes impracticable.

In U. S. Patent 1,762,172 to the present applicant and Joseph W. Brittonthere is disclosed a method directed to the preparation of aniline orphenylamine (C H .NH as well as various other ar lamines from thecorresponding halogenate benzene, for example, in the case of suchaniline from chlorobenzene, by a process of the general type describedabove wherein the reaction, however, is greatly promoted and a muchhigher yield of such arylamine obtained by addition to the reactionmixture of certain ingredients that apparently have the effect of acatalyst.

Briefly described the process consists in reacting the correspondinghalogenated hydrocarbon and aqueous ammonia solution in the presence ofa cuprous compound, whereby a mixture of arylamine and an aqueoussolution of various copper compounds and certain ammoniacal-coppercompounds is produced,

then adding a caustic compound to such mixture or to the respectiveaqueous and oily layers into which it separates upon standing, andthereafter in repeatin the process, using the precipitate resulting omthe action of the caustic compound on such copper compounds for thecuprous compound originally employed to promote the reaction.

In carrying out the foregoing process, or for that matter any processinvolving a reaction between a halogenated hydrocarbon and aqueousammonia solution, one of the side products formed in addition to the de-Application filed April 27, 1927. Serial 1T0. 187,121.

sired mono-arylamine is the corresponding diaryl compound, for exam 1cin the case of the process for making ani ine s ecificall a small amountof diphenylamine, C H z is formed as such a side product. Towhateverextent such side product is formed, the yield of the desired end productis of course reduced. 1

I have now discovered that, when the diaryla-mine thus produced isremoved from the reaction products and re-introduced into thesystemhalogenated benzene plus aqueous ammonia solution, it exercises amarked favorable influence upon the production of the desiredmono-arylamine. As a result the system is maintained in an approximatestate of balance with respect to such diarylamine and the yield of thedesired primary arylamine is measurably increased.

To the accomplishment of the foregoing and related ends, the invention,then, consists of the steps hereinafter fully described and particularlypointed out in the claims, the following description setting forth butone of the various ways in which the principle of the invention may beused.

The following is given as a specific example of the procedure involvedin carrying out the present improved method or process for the making ofaniline, viz

In starting the operation, a suitable quantity of chlorobenzene is mixedwith a. 25 to 30 per cent. aqueous ammonia solution in such amount as tofurnish from i'to 5 mol. of anhydrous ammonia to one mol. ofchlorobenzene. This mixture is then charged with from 0.1 to 0.2 mol. ofcuprous oxide, hydroxide, or chloride, or a mixture thereof, (thecuprous oxide or hydroxide being preferred) into a suitable closedreaction chamber, such as an iron autoclave capable of withstanding aworking pressure as high as several thousand pounds, and the mixturethereupon heated with stirring to a temperature of from 150 to 250degrees C. and with a corresponding pressure, viz, from 500 to 1500pounds. The time of heating will vary with the templerature and pressurethus applied from 12 ours for the lower temperature 10 to from 4 to 5hours at the higher temperature.

The general reaction that occurs may be represented by the followingequation, viz

A certain amount of henol will be simul taneously formed by-hy rolysisof the chlorobenzene and a small amount of diphenylamine, (C H .NH, isalso formed as a side product; while the excess ammonia will remain ofcourse, as well as any unreacted chlorobenzene. In addition to reactingwith the'latter, the ammonia and ammonium chloride react with thecuprous oxide, hydroxide,

or chloride introduced into the reaction mix-- ture as aforesaid toyield certain copper-ammoniacal compounds that, as indicated above,constitute upon proper treatment a catalyst possessing significantproperties.

Upon completion of the reaction in the first or main stage of theoperation, the products still in the form of a liquid mixture resultingtherefrom are discharged under pressure of the ammonia gas in theautoclave into a suit able closed vessel for removal first of the freeammonia and then for the treatment of the other ingredients in suchmixture as will now be described. These ingredients will include theaniline oil containing unreacted chlorobenzene with some phenol as Wellas some diphenylamine; also the water from the aqueee.

ous solution of ammonia which will contain ammonium chloride with anyexcess of ammonia present. There will also be dissolved in such aqueoussolution and to a certain extent in the aniline oil the above-mentionedcopper-ammoniacal compounds.

The treatment of the foregoing mixture of ingredients and productsresulting from the reaction for the recovery of the aforesaid catalyticmaterial forms no part of the present invention and need not be furtherdescribed than to state that it involves the addition either to theunseparated mixture, or to one or both of the oily and aqueous layersinto which such mixture separates upon standing, of a caustic compound,using this term to include the oxide, hydroxide or equivalent compoundof an alkaline earth metal as well as an alkali metal. After treatmenteither of the mixture as a whole or of the oily (aniline) layer withsuch caustic compound, the resulting material is next subjected todistillation, preferably steam distillation, with the result that thefollowing products are distilled off in the order stated, viz, the freedammonia, chlorobenzene, aniline and diphenylamine. By fractionating theaniline, not only may the aniline be separated from the chlorobenzene,but also well freed from diphen lamine and the latter separatelyrecovered fi om the two other products just named, although for resentprocess it may remain enzene which is desirably reinitial reaction foruse over the purpose of with the chloro turned to the again.

According to the present improved process, upon repeating the reactionbetween chlorobenzene and aqueous ammonia solution, a certain amount ofsuch recovered diphenylamine is returned or added thereto, it beingunderstood that once the operation has been established, such return isin effect continuously made and the amount of diphenylamine in thereaction mixture is thus at all times maintained at the point where anapproximate state of chemical balance with respect to suchvdiphenylamine exists. The formation of more di henylamine from thereacting ingredients 1s thus repressed to a marked extent; in otherwords, the amount of diphenylamine will not be measurably increased asit thus passes and re-passes through the system.

In conclusion it should be stated that my improved process which may bereferred to generally as a process for the ammonolysis of halogenatedaromatic hydrocarbons, is applicable not merely to aniline orphenylamine, C H .NH but to the production of the homologues of anilineor the various arylamines in general, as illustrated by the followingexamples, viz I 1. Dichlorobenzene, C H CI with ammonium cuprouschloride, and co per, readily yields O H (NH phenylene iamine.

2. Chlorotoluene, CH C H Cl, similarly yields CH O H NH toluidine.

3. Chloronaphthalene, C H-,Cl, similarly yields C H,NH naphthylamine.

4. Chloroanthraquinone, G H O CI, similarly yields O H O NHamino-anthraqui-. none.

Certain of the foregoing homologues of aniline or equivalent arylamines,it should further be explained, may not be separable by drydistillation, but in such case separation may be effected by anextraction process usin chlorobenzene or equivalent solvent Ot er modesof applying the principle of the invention may be employed, change being made as regards the details disclosed, I provided the steps statedin any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as myinvention 1. In a method of making a primary arylamine by reactingbetween the corresponding halogenated aromatic hydrocarbon and aqueousammonia, wherein a diarylamine tends to form along with the desiredcompound, the step which consists in adding such diarylamine to thereaction mixture.-

2. In a method of making a primary arylamineby reacting between thecorresponding halogenated aromatichydrocarbon and aqueous, ammonia,wherein a diarylamine tends to form along with the desired compound, thestep which consists in .adding such diarylamine to the reaction mixturein an amount sufficient to maintain the system in an approximate stateof chemical balance with respect to such diarylamine, whereby theformation of any substantial additional amount of the latter isprevented.

3. In a method of making a primary arylamine, the steps which consist inreacting betweenthe corresponding halogenated aromatic hydrocarbon andaqueous ammonia in the presence of an ammonolytic catalyst, with theproduction of the desired monoarylamine, and some diarylamine, removingand separating such arylamines, and returning the diarylamine to thefirst step.

4. In a method of making aniline by reacting between a mono-halogenatedbenzene and aqueous ammonia, wherein diphenylamine tends to form, thestep which consists in adding such diphenylamine to the reactionmixture.

5. In a method of making aniline by reacting between a mono-halogenatedbenzene and aqueous ammonia, wherein diphenylamine tends to form, theste which consists in adding such diphenylamlne to the reaction mixturein an amount sufiicient to maintain an approximate state of balance withrespect to such diphenylamine, whereby the formation of any substantialadditional amount of the latter is revented.

6. In a method of ma ing aniline, the steps which consist in reactingbetween a monohalogenated benzene and aqueous ammonia in the presence ofan ammonolytic catalyst, with the production of the desired aniline andsome diphenylamine, removing and se aratin such amines, and returningthe ipheny amine to the first step.

7. The method of making'aniline which comprises reacting betweenchlorobenzene and aqueous ammonia in the presence of a cuprous compound,and restraining the formation of diphenylamine from the reactioncomponents y initially adding such compound tothe reaction mixture.

of the desired aniline and some diphenylamine, removing1 and separatingsuch amines, and returning t e diphenylamme to the first step.

10. In a method involving the ammonolysis of a halogenated aromatichydrocarbon wherein, in addition to the desired primary amine product,another amino-compound tends to form in equilibrium with such desiredproduct, the step which consists in adding the undesired compound to thereacting ingredients.

11. In a method involving the ammonolysis of a halogenated aromatichydrocarbon, wherein, in addition to the desired primary amine productanother amino-compound tends to form in equilibrium with such desiredproduct, the step which consists in adding the undesired compound to thereacting ingredients in an amount sufiicient to maintam the system in anapproximate state of balance with respect to such compound.

12. In a method involving the ammonolysis of a halogenated aromatichydrocarbon, wherein, in addition to the desired primary amine productanother amino-compound tends to form in equilibrium with such desiredproduct, the step which consists in adding the undesired compound to thereacting ingredients in an amount a proximatin that in which suchcompoun would norma 1y form therein.

\ Signed by me this 25th day of April 1927.

' WILLIAM H. ILLIAMS.

8. The method of making aniline which,

comprises reacting between chlorobenzene and aqueous ammonia in thepresence of a cuprous compound, and restralning the formation ofdiphenylamine from the reaction components by initially adding suchcompound to the reaction mixture in an amountv sufiicient to maintain anapproximate state of balance with respect to such diphenylamine, wherebythe formation of any substantial additional amount of the latter isprevented.

9. In a method of making aniline, the steps which consist in reactingbetween chloro-benzene and aqueous ammonia in the presence of a cuprouscompound, with the production

